线粒体动力学及线粒体自噬调控机制的研究进展

线粒体形态和功能的异常与多种疾病的发生密切相关。线粒体通过不断的分裂和融合,维持线粒体网络的动态平衡,该过程称为线粒体动力学,是维持线粒体形态、分布和数量,保证细胞稳态的重要基础。此外,机体还通过线粒体自噬过程降解胞内功能异常的线粒体,维持线粒体稳态。线粒体动力学与线粒体自噬二者之间可相互调控,共同维持线粒体质量平衡。探讨线粒体动力学和线粒体自噬的调控机制对揭示多种疾病发生的分子机制、开发新的靶向线粒体动力学蛋白或线粒体自噬调控蛋白的药物具有重要意义。本文从线粒体动力学与线粒体自噬出发,对线粒体动力学调控机制、线粒体自噬及其发生机制以及二者的相互作用关系、线粒体动力学及线粒体自噬与人类相关疾病等方面作一综述。     

线粒体动力学调控机制及其在肾脏病理生理学中的作用

线粒体是一种动态变化的细胞器,它通过不断的融合、分裂来维持线粒体的形态、数量和功能稳定,这一过程称为线粒体动力学,是线粒体质量控制的重要机制。线粒体的过度融合与分裂都会导致线粒体动力学的稳态失衡,引起线粒体功能障碍,导致细胞损伤甚至死亡。肾脏的生理活动主要由线粒体供能,线粒体动力学稳态失衡影响着线粒体功能,与急性肾损伤、糖尿病肾病等肾脏疾病密切相关。本文对线粒体动力学的调节、线粒体动力学稳态失衡如何导致线粒体损伤以及线粒体损伤对肾脏病理生理学的影响进行综述,以加深对肾脏疾病中线粒体作用的理解与认识。     

运动调控衰老骨骼肌UPRmt和线粒体自噬互作的机制

衰老性肌萎缩中的线粒体功能障碍与线粒体未折叠蛋白反应(mitochondrial unfolded protein response,UPRmt)和线粒体自噬构成的线粒体质量控制(mitochondrial quality control, MQC)的损伤密切相关。线粒体质量控制是线粒体维持内环境稳态的保护机制，其中UPRmt和线粒体自噬分别负责受损线粒体的修复和清除。UPRmt应对未折叠蛋白应激，维持线粒体和细胞蛋白质稳态，延长寿命并调节代谢重构，而线粒体自噬选择性地去除受损严重的线粒体，两者共同维护线粒体稳态。本文总结UPRmt与线粒体自噬的互作、衰老骨骼肌UPRmt与线粒体自噬的变化和运动逆转衰老骨骼肌UPRmt和线粒体自噬的机制，重点总结运动源的活性氧(reactive oxygen species, ROS)调控UPRmt与线粒体自噬互作的信号通路研究进展，并为衰老性肌萎缩进程中线粒体质量控制的维持提供参考。     

线粒体超微结构及其调控机制的研究进展

线粒体超微结构是用电子显微镜观察到的精细结构,其可以根据不同能量需求和生理环境变化而变化,对线粒体功能具有关键调节作用.线粒体嵴结构是一种重要的线粒体超微结构,对多种线粒体疾病产生影响.因此,研究线粒体超微结构的调节机制,理解线粒体超微结构功能,对研究线粒体疾病的发病机理及寻找相关疾病的治疗靶点具有重要指导意义.本文详细介绍了线粒体嵴结构的主要调节机制,重点关注线粒体超微结构组成成分、线粒体超微结构对线粒体功能的影响、线粒体超微结构与线粒体疾病关系方面的研究进展,以期为制定更有效的线粒体疾病治疗方案提供理论参考.     

线粒体钙离子转运的研究进展

线粒体内的钙离子浓度对于线粒体的ATP合成、线粒体通透性转变孔道的开放及细胞质内钙信号的调节具有重要影响。线粒体的钙离子转运调节平衡是线粒体除合成ATP和诱导细胞凋亡以外的又一重要功能。线粒体中存在钙吸收和钙释放两种重要的钙转运机制。文章就线粒体外膜钙离子的转运、内膜钙离子的吸收和释放等线粒体钙离子转运方式的研究历史和最新研究进展进行了综述。     

线粒体ATP敏感钾通道与钙激活钾通道激活对正常与缺血脑线粒体通透性转变的影响

目的：明确线粒体ATP敏感钾通道与钙激活钾通道对正常和缺血脑线粒体渗透性转变的作用。方法：实验采用分光光度法,在分离的线粒体上分别观察两种线粒体钾通道激动剂对正常与缺血脑线粒体肿胀的影响。结果：在正常脑线粒体,diazoxide与NSl619能有效抑制由钙诱导的线粒体氏20下降,但其效应可被atractyloside所阻断。与正常相比,缺血损伤后的脑线粒体在钙离子诱导下线粒体A520下降较快,diazoxide与NS1619仍可抑制由钙诱导的线粒体A520下降,其作用同样为atractykxside所阻断。结论：线粒体ATP敏感钾通道与钙激活钾通道激活在离体条件均具有保护脑线粒体的作用,其作用可能是通过影响线粒体通透性转变而实现。     

线粒体转录终止因子蛋白家族研究进展

线粒体转录终止因子蛋白的作用是与线粒体DNA的特异位点结合,导致线粒体基因转录停止。近年来,随着人们对线粒体基因转录机制和人线粒体疾病的深入研究,线粒体转录终止因子的功能开始受到人们的关注。本文介绍了线粒体转录终止因子及其家族成员的研究进展和有待解决的一些问题。     

PINK1/parkin通路调控线粒体自噬机制的研究进展

线粒体自噬指细胞通过自噬机制选择性除去损伤或多余的线粒体。真核生物通过线粒体自噬调控线粒体质量,维持供能细胞器的功能。大量研究表明,帕金森病相关基因PINK1和parkin可通过线粒体自噬参与并维持线粒体功能。PINK1与parkin能协同特异性识别损伤的线粒体,PINK1作为线粒体质量调控的探测器被活化,此过程中泛素化酶和去泛素化酶对维持parkin活性及线粒体自噬的效率有重要作用。本文主要总结PINK1/parkin通路在线粒体自噬中的功能与作用。     

线粒体蛋白质组学研究进展

线粒体是真核生物中重要的细胞器,其包含的全部蛋白质称为线粒体蛋白质组。人类线粒体大约包含1500多种蛋白质,由核基因和线粒体基因共同编码。线粒体是细胞能量合成和物质代谢的中心,其功能障碍将直接或问接引起许多疾病。目前线粒体蛋白质组学正是系统性地研究线粒体在生理、病理过程中的功能变化以及研究疾病发生机制的重要方法。将线粒体蛋白质组的研究方法、研究进展、线粒体蛋白质组的性质及其在相关疾病研究中的作用进行综述,并对线粒体蛋白质组学在疾病发生机制和诊断治疗中的发展前景进行展望。     

帕金森病相关蛋白PINK1和Parkin通过降解Miro影响线粒体运动

帕金森病是一种常见的神经退行性疾病,发病机制尚不清楚,线粒体功能障碍是可能的原因之一。帕金森病相关蛋白PINK1和Parkin均被证明影响线粒体功能和形态,并参与线粒体质量监控。2011年11月《细胞》杂志 （Cell）147期 发表了题为《PINK1和Parkin导致Miro磷酸化降解和线粒体运动阻滞》的文章,发现PINK1 / Parkin 通路可以作用于定位在线粒体外膜的线粒体移动相关蛋白Miro,PINK1直接磷酸化Miro,Parkin参与Miro降解,使受损线粒体脱离微管,从而阻滞线粒体运动。作者猜测这一过程能够隔离受损线粒体,避免了受损线粒体在细胞中的扩散。该研究深入探讨了PINK1和Parkin相互作用机制,揭示了线粒体质量控制系统如何直接调控线粒体运输,提出了受损线粒体的不正常运输可能是PD的致病原因。     

Comparison of the effect of temperature on kidney cortex mitochondria from rabbit,dog, pig,and human: Arrhenius plots of ADP-stimulated respiration

The effect of temperature on the rate of ADP-stimulated respiration of mitochondria from dog, rabbit, pig, and human kidney cortex mitochondria was plotted according to the Arrhenius relationship. The temperature at which the plot demonstrated a break was at 15 °C for mitochondria from dog, pig, and human kidneys. The discontinuity occurred at 10 °C or less for mitochondria from rabbit kidneys. This difference suggests that mitochondria from rabbit kidneys undergo a lipid-phase transition at lower temperatures than for other species commonly used in experimental renal preservation. The implications of this difference suggest caution in using results obtained with rabbit kidneys for comparison to results obtained from hypothermic renal preservation of other species kidneys. Apparent fluidization of dog kidney mitochondrial membranes with adamantine abolished the discontinuity in the Arrhenius plot.     

Mitochondrial configurations in peripheral nerve suggest differential ATP production

Physiological states of mitochondria often correlate with distinctive morphology. Electron microscopy and tomographic reconstruction were used to investigate the three-dimensional structure of axonal mitochondria and mitochondria in the surrounding Schwann cells of the peripheral nervous system (PNS), both in the vicinity of nodes of Ranvier and far from these nodes. Condensed mitochondria were found to be abundant in the axoplasm, but not in the Schwann cell. Uncharacteristic of the classical morphology of condensed mitochondria, the outer and inner boundary membranes are in close apposition and the crista junctions are narrow, consistent with their function as gates for the diffusion of macromolecules. There is also less cristae surface area and lower density of crista junctions in these mitochondria. The density of mitochondria was greater at the paranode–node–paranode (PNP) as was the crista junction opening, yet there were fewer cristae in these organelles compared to those in the internodal region. The greater density of condensed mitochondria in the PNS axoplasm and in particular at the PNP suggests a need for these organelles to operate at a high workload of ATP production.     

Rat kidney mitochondrial carbonic anhydrase

Mitochondrial carbonic anhydrase has previously been quantitated in liver mitochondria; it was not detected in guinea pig kidney cortical mitochondria. Evidence of this enzyme in rat kidney cortical mitochondria is reported. Electron microscopy showed that intact mitochondria were free of other intracellular organelles. When intact kidney mitochondria were added to isotonic 3'-(N'-morpholino) propanesulfonic acid buffer with 25 mM KHCO3 (1% labeled with 18O) the rate of disappearance of C18O16O was biphasic; this indicates that there is carbonic anhydrase within the inner mitochondrial membrane. Intact rat kidney mitochondria were assayed for carbonic anhydrase activity at 4 degrees C by the changing pH technique. The rate of CO2 hydration in the presence and absence of intact mitochondria was identical; this rate increased when Triton X-100 was added which indicates that all carbonic anhydrase is inside the inner mitochondrial membrane. Carbonic anhydrase activity was quantitated as kenz (units, ml.s-1 mg-1 mitochondrial protein) at 37 degrees C, pH 7.4, in 25 mM NaHCO3 (1% labeled with 18O) by following the rate of disappearance of C18O16O from solutions before and after addition of disrupted mitochondria. Values of Kenz for liver and kidney mitochondria from rats given free access to normal rat chow and water at neutral pH were 0.06 and 0.08 (respectively). Values of kenz for liver and kidney mitochondria from rats fed as above and with free access to water adjusted to pH 2.5 with HCl were 0.04 and 0.16, respectively. Values of kenz for rats starved for 48 h were 0.06 and 0.12 (respectively). The values of kenz remained 0.11-0.14 in liver mitochondria from guinea pigs fed normally, given dilute acid, or starved and the value was always at zero in guinea pig kidney mitochondria. Values of Kenz were measured with disrupted mitochondria by the 18O technique as a function of pH at 25 degrees C, 25 to 75 mM NaHCO3, ionic strength 0.3. From pH 7.0 to 8.0 kenz increased threefold for mitochondria from rat liver, fed rat kidney, and acid rat kidney, and increased eightfold for mitochondria from guinea pig liver. kenz was decreased similarly by increasing HCO3- in mitochondria from rat liver, fed kidney, and acid kidney; it is concluded that carbonic anhydrase in rat liver mitochondria is probably the same isozyme as in rat kidney mitochondria. The published observation that rat kidney cortices are up to 10 times as gluconeogenic from pyruvate as guinea pig kidney cortices can be explained by the presence of mitochondrial carbonic anhydrase in rat but not guinea pig mitochondria.     

Studies on the energy release of rice mitochondria under different conditions by means of microcalorimetry

The thermodynamic and kinetic behaviors of energy release of mitochondria isolated from rice (Oryza sative L.) were studied by using a LKB 2277 Bioactivity Monitor under different conditions. The thermogenesis curves of energy release of the rice mitochondria (which had been kept at 0-3 degrees C for 15 h and 40 day before the determination) were determined respectively at 25 and 30 degrees C, and the difference in shape of the thermogenesis curves and thermodynamic and kinetic characteristics were compared. The thermodynamic and kinetic parameters of energy release of the mitochondria in the thermogenesis increasing stage have been calculated, and the experimental thermokinetic equations of the thermogenesis have been established. The results indicated that the lower the temperature, the slower the energy release of the rice mitochondria. Both the thermogenesis and the energy release rate of the rice mitochondria increased after the mitochondria was kept at lower temperature for 40 days. One can use the methods to characterize the ability of the rice mitochondria to release energy under different conditions.     

Pathway of glutamate oxidation and its regulation in the HuH13 line of human hepatoma cells.

Well-coupled mitochondria were isolated from a HuH13 line of human hepatoma cells and human liver tissue. The liver mitochondria showed a feeble glutamine oxidation activity in contrast to the hepatoma mitochondria, whereas they utilized glutamate well for the oxidative phosphorylation. In the liver mitochondria, glutamate was oxidized via the routes of transamination and deamination. On the other hand, glutamate oxidation was initiated preferentially via transamination pathway in the tumor mitochondria. In the liver mitochondria, bicarbonate nearly at a physiological concentration inhibited oxygen uptake with glutamate as substrate. The interaction of bicarbonate with the pathway of glutamate oxidation occurred primarily at the level of succinate dehydrogenase, due to competitive inhibition of the enzyme by the compound. In contrast to the liver mitochondria, glutamate oxidation was not affected by bicarbonate in the tumor mitochondria. These results indicate that the aberrations in the glutamate metabolism and its regulation observed in the hepatoma mitochondria may be favorable to the respiration utilizing glutamine and/or glutamate as an energy source.     

Structural and functional features and significance of the physical linkage between ER and mitochondria

The role of mitochondria in cell metabolism and survival is controlled by calcium signals that are commonly transmitted at the close associations between mitochondria and endoplasmic reticulum (ER). However, the physical linkage of the ER-mitochondria interface and its relevance for cell function remains elusive. We show by electron tomography that ER and mitochondria are adjoined by tethers that are approximately 10 nm at the smooth ER and approximately 25 nm at the rough ER. Limited proteolysis separates ER from mitochondria, whereas expression of a short "synthetic linker" (<5 nm) leads to tightening of the associations. Although normal connections are necessary and sufficient for proper propagation of ER-derived calcium signals to the mitochondria, tightened connections, synthetic or naturally observed under apoptosis-inducing conditions, make mitochondria prone to Ca2+ overloading and ensuing permeability transition. These results reveal an unexpected dependence of cell function and survival on the maintenance of proper spacing between the ER and mitochondria.     

Photodesorption of mitochondria

Photodesorption of mitochondria absorbed on a quartz plate was discovered. The rate of photodesorption of mitochondria from the plate into solution depends on the wavelength, intensity, and irradiation period. The maximum rate of photodesorption was detected upon irradiation with UV light at the mitochondrial protein tryptophan absorption band. UV photodesorption is presumably caused by a local photothermal effecth—eating of photoexcited proteins at the membrane surface that attach mitochondria to the plate. Preliminary fixation of a smear with isopropanol or acetone drastically decreased photodesorption and spontaneous desorption. No photodesorption of either mitochondria or formazan was observed upon illumination with green light of formazan granules formed in mitochondria as a product of reductase reaction. These data are important for elaborating a technique of immobilizing mitochondria for enzyme assays and biosensors.     

The distribution of DNA among dividing mitochondria of Tetrahymena pyriformis

A squash technique was developed for log phase Tetrahymena pyriformis which permitted the resolution of over 100 individual mitochondria from a single cell. Mitochondria incorporated thymidine at all stages of the cell cycle, even when nuclear DNA synthesis was not occurring. During the stage of macronuclear DNA synthesis, however, there was a significant increase in the extent of mitochondrial labeling. Low radioautograph background suggests that mitochondrial DNA is synthesized at the mitochondria themselves. All mitochondria incorporated thymidine-3H within one population-doubling time. Grain counts also showed that the amount of mitochondrial label was retained for four generations and that this label remained randomly distributed among all mitochondria during this time. The results are not consistent with any theory of de-novo or "microbody" origin of mitochondria, but do support the hypothesis that mitochondria are produced by the growth and division of preexisting mitochondria. The stability of the mitochondrial DNA and its distribution among daughter mitochondria satisfy two prerequisites for a genetic material. The possibility is discussed that some of the genetic information for the mitochondrion is contained in the DNA associated with this organelle.     

Studies on the efflux of metalloporphyrin from isolated rat liver mitochondria. Effect of respiratory substrates and metabolic inhibitors.

Intramitochondrially synthesized Co-deuteroporphyrin is released to the incubation medium at a rate inversely correlated to the energy state of the mitochondria; i.e. the rate of efflux increases when substrate is depleted, respiration inhibited or the mitochondria are uncoupled. The efflux of Co-deuteroporphyrin from mitochondria remains low as long as the residual membrane potential is above one-third that of maximally energized mitochondria. Globin enhances the efflux of Co-deuteroporphyrin not only from mitochondria depleted of substrates [Husby & Romslo (1980) Biochem. J. 188, 459-465], but also from maximally energized mitochondria. The results provide further evidence for a co-operative mechanism between the mitochondria and their surroundings for the mobilization of metalloporphyrin from mitochondria.     

Oxygen consumption by mitochondria from an endotherm and an ectotherm

Comparisons of metabolic properties of mitochondria from an endothermic and an ectothermic vertebrate were performed. Oxygen (O2) consumption rates of liver mitochondria from laboratory mice and western fence lizard (Sceloporus occidentalis) were determined over a range of temperatures (10, 20, 30 and 37 degrees C) and in the presence of a variety of substrates. At 37 degrees C the O2 consumption rate of mouse mitochondria was 4-11 times higher than lizard mitochondria in the presence of five of eight substrates. This range of differences is similar to differences reported for O2 consumption of endothermic animals, tissues and cells over those of ectotherms. Thermal sensitivity of mitochondria was measured by calculation of Q10s for O2 consumption. Q10s were highest for mouse mitochondria overall. The range that showed the highest Q10s for the mouse mitochondria was 30-20 degrees C, whereas for the lizard mitochondria it was 20-10 degrees C. Thus, mitochondria from the ectotherm showed a lower degree of temperature sensitivity than did mitochondria from the endotherm. The preferred substrate for all mitochondria at all temperatures was succinate, but mouse mitochondria then showed some preference for alpha-ketoglutarate and citrate, whereas lizard mitochondria showed a preference for pyruvate and malate + pyruvate.